A number of poly (aryl ether sulfones) have been known for many years. They are linear polymers possessing a number of desirable features such as excellent high temperature resistance, good electrical properties, and toughness. One commercially important group of poly (aryl ether sulfones) are those containing a biphenyl group or moiety, typically derived from the monomer, 4,4'-biphenol. Poly (aryl ether sulfones) which contain the biphenyl, also called biphenylene group, are available from BP Amoco Polymers, Inc. under the tradename of Radel.RTM. Radel R.RTM., one of such Radel.RTM. materials, has the structure 1 and has ##STR1##
a Tg of about 220.degree. C. and is suitably made by the nucleophilic polycondensation of 4,4' -biphenol with 4,4'-dichlorodiphenyl sulfone as described, for example, in U.S. Pat. Nos. 4,108,837 and 4,175,175. Poly (aryl ether sulfones) which contain at least in part the 4,4'-biphenyl moiety, e.g., derived from 4,4'-biphenol, and also called the 4,4'-biphenylene moiety, are hereinafter referred to as poly (biphenyl ether sulfones). Due to their excellent mechanical and other properties, poly (biphenyl ether sulfones) can be used to manufacture a variety of useful articles such as molded articles, films, sheets and fibers.
It also offers high chemical and solvent resistance. Hence, it is particularly useful for manufacturing articles that are exposed to solvents or chemical agents at elevated temperatures and for extended times. Thus, poly (aryl ether sulfones) find application in articles such as medical trays which are subjected to repeated and rigorous sterilization procedures.
Many of the important articles made from poly (biphenyl ether sulfones) are manufactured by injection or other molding process. Although the currently available poly (biphenyl ether sulfones) have been very successful for the manufacture of molded articles, it would be desirable to have a poly (biphenyl ether sulfone) that has melt flow characteristics so that molding operations can be performed with improved flow and molding performance. This invention provides for such improved poly (biphenyl ether sulfones). The poly (biphenyl ether sulfones) of this invention have improved polydispersity, a lower level of undesirable low molecular weight oligomeric components and have improved melt flow properties compared to existing poly (biphenyl ether sulfones).
Although the improved poly (biphenyl ether sulfones) of this invention are not limited by the manner in which the poly (biphenyl ether sulfones) are prepared, we have determined that poly (biphenyl ether sulfones) having improved polydispersity and reduced amounts of low molecular weight oligomeric materials can be prepared by adjusting the concentration of the monomer reactants in a solution polymerization reaction that can be used to make poly(biphenyl either sulfones). By conducting the solution polymerization reaction at relatively high concentrations, thereby forming a polymerization reaction mixture with high polymer solids content, the improved poly (biphenyl ether sulfones) of this invention can be prepared.